1. Field Of The Invention
This invention relates to a method and apparatus for inactivating infectious agents in and resisting coagulation of biological fluids, and more particularly to providing antibodies in evacuated tubes before the biological fluid is introduced into the tube.
2. Description Of The Prior Art
In the evaluation and care of patients, it is often necessary to obtain blood samples. The routine procedure for drawing blood from a patient requires a needle holder, a disposable needle, and multiple evacuated tubes. A disposable needle is attached to the holder, the needle is inserted into the patient's vein and the evacuated tube is inserted through the opposite end of the needle into the holder. The evacuated tube is then allowed to receive the derived quantity of blood. The tube is then removed and another may be employed, if desired.
During the above process, the health care worker may be exposed to blood which drips from the end of the needle or may be injured by sticking the needle into his or her skin. In addition, the cap may accidentally come off of the tube or the tube may break, splashing the health care worker with blood. Laboratory workers, also, are exposed to the blood in the process of handling the blood filled tube and in disposing of the needle.
If a patient's blood contains infectious agents, health care workers may be exposed to these infectious agents and thus are at risk of acquiring infection. The Center For Disease Control has estimated that 500 to 600 health care workers are hospitalized annually due to occupationally acquired Hepatitis B Virus ("HBV"). U.S. Dept. of Labor and U.S. Dept. of Health and Human Services, Joint Advisory Notice on Protection Against Occupational Exposure to HBV and HIV, pages 1-13 Oct. 30, 1987. Of these, over 200 deaths resulted. Other infectious agents, such as Human Immunodeficiency Virus ("HIV"), Human T Lymphotropic Virus I ("HTLV I"), and Cytomegalovirus ("CMV") cause infections less often, but still pose a significant threat to the health care worker.
It is known to provide a blood collection tube and method that attempts to disinfect infectious viral contaminants instantaneously when the blood is taken. U.S. Pat. No. 4,675,159 discloses using a disinfectant material, such as aldehyde (with gluteraldehyde being preferred), in connection with a blood collection tube. The amount of aldehyde based disinfectant positioned in the container is adjusted to provide an ultimate concentration of aldehyde in the blood specimen of about 0.1 to 2.5 percent by weight and is buffered to a pH of about 7.2 to 8.5 percent. The aldehyde based substances disinfect blood by cross-linking and/or polymerizing amino groups on the surface of the infectious agent.
The problem with using aldehyde based substances is that the above-described polymerization distorts and destroys the structure and function of proteins. When used in biologic situations, a gluteraldehyde, for example, does not distinguish between the amino groups of infectious agents and the amino groups of the patient's blood and serum proteins. Ultimately, this cross-linking leads to coagulation which renders the blood sample unsuitable for routine processing. Also, the patient's altered proteins are unsuitable for analysis. Lowering of gluteraldehyde concentrations is not a solution because of the loss of ability to inactivate the infectious agents.
Other disadvantages of aldehyde based disinfectants are that they are unstable and that they cannot be used with heparin.
U.S. Pat. No. 4,308,232 discloses an anticoagulant stopper coating which resists adherence of cells to the stopper. The coating consists of a blood anticoagulant, a binding agent layer, and an outer layer of silicone oil.
U.S. Pat. No. 3,890,955 discloses a vacuum indicator. A standard blood collection tube having a partial vacuum pressure and a needle for removing blood from a patient is provided. A material, which is coated on the tube, changes color to indicate when vacuum pressure is lost in the tube.
U.S. Pat. No. 3,901,219 discloses a blood collecting container and method consisting of a tube having a stopper and a piston barrier which holds a chemical which can be added to the collected blood. When blood is introduced into the tube, the piston barrier descends (FIG. 2) until reaching constriction. FIG. 3 illustrates the apparatus with collected blood after it has been centrifuged.
Despite these known apparatus and methods there still remains a need for an effective way to prevent accidental infection of health care workers.
It is also desired, in evaluating blood constituents such as blood gases and potassium, to obtain an anticoagulated specimen. It is known to add EDTA (or equivalent chemical agents such as oxylate and citrate) or heparin to the drawn blood to obtain an anticoagulated specimen. The EDTA chelates calcium ions. These calcium ions are necessary for the functioning of many of the blood clotting factors (factors II, V, VII, VIII, IX and X). By removing the calcium, the effective functioning of the blood clotting factors is inhibited and the blood does not clot. Heparin functions through interaction with Antithrombin III and binding to factors XII, XI, IX, X and II. The binding inhibits the functioning of the factors and resists coagulation.
The problem with using chelating agents such as EDTA is that these cause water to leave cells and enter the plasma which causes mild dilution of the plasma. In addition, chelating agents cannot be used for blood gas determinations and when ions, such as calcium, are desired to be measured.
Heparin, which is a heterogenous mixture of linear and ionic polyelectrolytes, is not uniform in its effects. Heparin preparations have ranging solubilities and anticoagulative properties, and so must be used in excess to achieve reproducible coagulation. Heparin also precipitates fibronectin, a blood protein, which clogs the small orifices of blood gas instruments. Heparin binds calcium and therefore is not suitable for ionized calcium determinations. Likewise, heparin may bind certain antibiotics such as aminoglycosides.
Thus, there remains a need for a method and apparatus for inactivating infectious agents in and resisting coagulation of biological fluids. This method should not only effectively disinfect infectious agents, but also not adversely affect the other constituents of the particular biological fluid to be analyzed. There also remains a need for a method of resisting coagulation of biological fluids that can allow effective analysis of certain blood constituents such as blood gases and potassium.